Transceiver device and communication control device for a user station of a serial bus system, and method for communicating in a serial bus system

ABSTRACT

A transceiver device, communication control device, and method for a user station of a serial bus system. The transceiver device includes a first terminal for receiving a transmission signal from a communication control device, a transmission module for transmitting the transmission signal onto a bus, a reception module for receiving the signal from the bus, the reception module configured to generate a digital reception signal from the signal received from the bus, a second terminal for sending the digital reception signal to the communication control device and for receiving an operating mode changeover signal from the communication control device, and a changeover feedback block for outputting feedback regarding a changeover of the operating mode that has taken place based on the operating mode changeover signal. The changeover feedback block is configured to output the feedback to the communication control device via the second terminal and in the digital reception signal.

FIELD

The present invention relates to a transceiver device and acommunication control device for a user station of a serial bus system,and a method for communicating in a serial bus system that operates witha high data rate and a high level of error robustness.

BACKGROUND INFORMATION

For the communication between sensors and control units, for example invehicles, a bus system is frequently used in which data are transferredas messages under the ISO 11898-1:2015 standard, as a CAN protocolspecification with CAN FD. The messages are transferred as analogsignals between the bus users of the bus system, such as the sensor,control unit, transducer, etc.

Each bus user of the bus system is connected to the bus using atransceiver device. At least one reception comparator is provided in thetransceiver device which receives the analog signals from the bus andconverts them into a digital signal. The content of the digital signalmay be interpreted by a communication control device with the aid of itsprotocol controller. In addition, the communication control device maycreate a signal for the transfer on the bus and send it onto the bus,using the transceiver device. In this way, pieces of information areexchangeable between the bus users.

To allow data to be transferred at a higher bit rate via the bus thanwith CAN, an option has been provided in the CAN FD message format andin the CAN XL message format for changing over to a higher bit ratewithin a message. In such technologies, the maximum possible data rateis increased in comparison to CAN by using higher clocking in the areaof the data fields. For CAN FD frames or CAN FD messages, the maximumpossible data rate is increased beyond a value of 1 Mbit/s. In addition,the useful data length is expanded from 8 bytes to up to 64 bytes. Thesame applies for CAN XL, in which the speed of the data transfer is tobe increased into the range of 10BASE-T1S Ethernet, for example, and theuseful data length of up to 64 bytes thus far achieved with CAN FD isintended to be greater. The robustness of the CAN- or CAN FD-basedcommunications network may thus be advantageously maintained.

For the transfer at the higher bit rate, the previous operating mode ofthe transceiver device is to be changed over from an operating mode forthe transfer at the lower bit rate (operating mode Z_SL) into anotheroperating mode. It should be noted that during the transfer at thehigher bit rate, only one of the user stations of the bus system is thesender of the message, whereas all other user stations are onlyreceivers of the message. Therefore, for the signaling of operating modeZ_F, for the higher bit rate a distinction is made as to whether theuser station is only the receiver (operating mode Z_F_RX) or also thesender (operating mode Z_F_TX) in order to appropriately switch theoperating mode of its transceiver device.

It is possible for the communication control device to signal to thetransceiver device the information concerning which operating mode thetransceiver device is to be switched into. As a result, however, it isnot known to the communication control device whether the transceiverdevice even notices the signaling of the changeover of the operatingmode at all, and whether the transceiver device correctly interprets orimplements the signaling of the changeover of the operating mode.

SUMMARY

An object of the present invention is to provide a transceiver deviceand a communication control device for a user station of a serial bussystem, and a method for communicating in a serial bus system, whichsolve the above-mentioned problems. In particular, an object is toprovide a transceiver device and a communication control device for auser station of a serial bus system, and a method for communicating in aserial bus system in which the changeover of the operating mode of thetransceiver device may be carried out with high robustness, and alsothat the carrying out is checkable with little expenditure of time andcosts.

The object may be achieved by a transceiver device for a user station ofa serial bus system in accordance with the present invention. Inaccordance with an example embodiment of the present invention, thetransceiver device includes a first terminal for receiving atransmission signal from a communication control device, a transmissionmodule for transmitting the transmission signal onto a bus of the bussystem, in which bus system at least one first communication phase andone second communication phase are used for exchanging messages betweenuser stations of the bus system, a reception module for receiving thesignal from the bus, the reception module being designed to generate adigital reception signal from the signal received from the bus, a secondterminal for sending the digital reception signal to the communicationcontrol device and for receiving an operating mode changeover signalfrom the communication control device, and a changeover feedback blockfor outputting feedback regarding a changeover of the operating modethat has taken place as a result of the operating mode changeoversignal, the changeover feedback block being designed to output thefeedback to the communication control device via the second terminal andin the digital reception signal.

In the reception signal, the transceiver device may provide feedback tothe communication control device, via the second terminal that isalready present, as to whether the transceiver device has noticed thesignaling of the changeover of the operating mode, and how the signalinghas been interpreted. On this basis, the communication control devicemay check whether or not the transceiver device is correctly switchedfor the present operating state or the present communication phase. Thechangeover of the operating mode of the transceiver device is thuscheckable, which increases the robustness of the bus system. The reasonis that in the event of an error, the communication control device mayrespond in a targeted manner since it is aware of the problem.

Furthermore, an additional terminal or a protocol controller for thetransceiver device is not necessary. All of this saves significantsilicon surface area, and thus saves on resources, space, and costs.

The feedback of the changeover of the operating mode to thecommunication control device also makes it possible for thecommunication control device to respond appropriately in the event oferror. For example, the communication control device may send an errorframe in order to abort the transfer of the frame. The transfer usingincorrectly set bus components may thus be discontinued as quickly aspossible. This increases the net data rate that is transferable in thebus system, and the communication in the bus system becomes more robust.

In accordance with an example embodiment of the present invention, thefeedback of the changeover of the operating mode to the communicationcontrol device assists with troubleshooting, since the communicationcontrol device knows whether the transceiver device was able to changethe state. The communication control device may also indicate viasoftware that the connected communication control device already has notbeen able to carry out the changeover K times, where K is a naturalnumber including 0. The value of K may be seen as an indication of howsoon the transceiver device might fail. To prevent the failure, thetransceiver device may then be replaced in a timely manner in a repairshop prior to the failure. This increases the safety of the system inwhich the bus system is used.

In addition, by use of the transceiver device, in one of thecommunication phases, an arbitration from CAN may be maintained whilestill increasing the transfer rate considerably compared to CAN or CANFD. This may be achieved by using two communication phases havingdifferent bit rates, and making the start of the second communicationphase, in which the useful data are transferred at a higher bit ratethan in the arbitration, clearly identifiable and checking them for thetransceiver device. As a result, a substantial increase in the bit rate,and thus in the transfer speed from the sender to the receiver, isachievable. However, at the same time a high level of error robustnessis ensured.

-   -   In accordance with an example embodiment of the present        invention, the method carried out by the transceiver device may        also be used when at least one CAN user station and/or at least        one CAN FD user station that send(s) messages according to the        CAN protocol and/or CAN FD protocol are/is also present in the        bus system.

Advantageous further embodiments of the transceiver device are disclosedherein.

In accordance with an example embodiment of the present invention, thechangeover feedback block may include an operating mode detection modulefor detecting, based on the output signals of the transmission moduleand of the reception module, which operating mode the transmissionmodule and the reception module are switched into, and an operating modefeedback module for evaluating an operating mode status signal that isoutput by the operating mode detection module, using a status signal ofan operating mode changeover block that is designed to carry out thechangeover of the operating mode based on the operating mode changeoversignal.

The operating mode feedback module may be designed to decide whether theoperating mode feedback module must provide feedback to thecommunication control device via the digital reception signal, and whenthe feedback must be sent.

According to one particular embodiment of the present invention, theoperating mode feedback module may be designed to insert the feedbackinto the digital reception signal after the changeover of the operatingmode that has been signaled via the operating mode changeover signal.

According to another particular embodiment of the present invention, theoperating mode feedback module may be designed to insert the feedbackinto the digital reception signal after the operating mode changeoversignal but before the changeover of the operating mode that has beensignaled via the operating mode changeover signal.

It is possible for the operating mode feedback module to be designed toinsert the feedback into the digital reception signal as at least onepulse having a value that is the inverse of a value of the digitalreception signal. The pulse may have a predetermined absolute duration.Alternatively, the pulse is designed in such a way that the pulse in thedigital reception signal overwrites a value whose duration in thedigital reception signal is limited by the distance between twoarbitrary edges in the digital reception signal.

The at least one pulse may last at the bus up to a subsequent edgechange that follows in the digital reception signal.

Alternatively, it is possible for the operating mode feedback module tobe designed to configure the feedback as manipulation of the digitalreception signal in such a way that the digital reception signal has aconstant value up to a predetermined event. The predetermined event maybe a new signaling of the changeover of the operating mode, using theoperating mode changeover signal, or a predetermined passage of time inthe transceiver device.

The transceiver device may also include an operating mode changeoverblock for evaluating the operating mode changeover signal that isreceived from the communication control device at the second terminaland for evaluating the transmission signal, the operating modechangeover block being designed to switch the transmission module and/orthe reception module into one of at least three different operatingmodes based on a result of the evaluation.

The operating mode changeover signal received from the communicationcontrol device at the second terminal is possibly at least one pulsehaving a value that is the inverse of a value of the digital receptionsignal, the operating mode changeover block being designed to switch thereception module from the first operating mode into the second operatingmode when the changeover signal includes the pulse, and the value of thetransmission signal corresponds to the value of the pulse, the operatingmode changeover block being designed to switch the transmission moduleand the reception module from the first operating mode into the thirdoperating mode when the changeover signal includes the pulse, and thevalue of the transmission signal is the inverse of the value of thepulse. It is possible for the transceiver device in the second operatingmode to not be the sender of the message in the second communicationphase, and for the transceiver device in the third operating mode to bethe sender of the message in the second communication phase.

Moreover, the object stated above may be achieved by a communicationcontrol device for a user station of a serial bus system having thefeatures of the present invention. In accordance with an exampleembodiment of the present invention, the communication control deviceincludes a communication control module for generating a transmissionsignal for controlling a communication of the user station with at leastone other user station of the bus system, in which bus system at leastone first communication phase and one second communication phase areused for exchanging messages between user stations of the bus system, afirst terminal for sending the transmission signal to a transceiverdevice which is designed to transmit the transmission signal onto a busof the bus system, a second terminal for receiving a digital receptionsignal from the transceiver device, the communication control devicebeing designed to generate an additional signal that indicates to thetransceiver device that a switch is to be made from the presentoperating mode into another operating mode of at least two differentoperating modes, and that achieves an internal communication between thecommunication control module and the transceiver device, and thecommunication control module being designed to send the additionalsignal, in the digital reception signal, to the transceiver device viathe second terminal, and to receive, via the second terminal, feedbackin the digital reception signal from the transceiver device regarding achangeover of the operating mode that has taken place as a result of theoperating mode changeover signal, and to evaluate the feedback.

The communication control device yields the same advantages as statedabove with regard to the transceiver device.

In accordance with an example embodiment of the present invention, thetransmission module is possibly designed to drive bits of the signalsonto the bus in the first communication phase with a first bit time thatis longer by at least a factor of 10 than a second bit time of bits thatare driven by the transmission module onto the bus in the secondcommunication phase. The operating mode changeover signal, via thesecond terminal for signaling that the changeover of the operating modeis to be made, may include at least one pulse with a duration that isshorter than the first bit time and longer than the second bit time, orat least one pulse with a pulse duration that is approximately equal tothe second bit time or shorter than the second bit time. In addition,the feedback via the second terminal for signaling that the operatingmode has been changed over may include at least one pulse with aduration that is shorter than the first bit time and longer than thesecond bit time, or at least one pulse with a pulse duration that isapproximately equal to the second bit time or shorter than the secondbit time.

According to one option, the signal received from the bus in the firstcommunication phase is generated with a different physical layer thanthe signal received from the bus in the second communication phase.

It is possible that in the first communication phase, it is negotiatedwhich of the user stations of the bus system in the subsequent secondcommunication phase obtains, at least temporarily, exclusive,collision-free access to the bus.

The above-described transceiver device and the above-describedcommunication control device may be part of a user station of a bussystem which also includes a bus and at least two user stations that areconnected to one another via the bus in such a way that they maycommunicate serially with one another. At least one of the at least twouser stations includes an above-described transceiver device and anabove-described communication control device.

Moreover, the object stated above may be achieved by a method forcommunicating in a serial bus system according to the present invention.In accordance with an example embodiment of the present invention, themethod is carried out using a transceiver device of a user station for abus system in which at least one first communication phase and onesecond communication phase are used for exchanging messages between userstations of the bus system, the user station including a transmissionmodule, a reception module, a changeover feedback block, a firstterminal, and a second terminal, and the method including the steps ofreceiving, via the reception module, a signal from the bus of the bussystem, generating, via the reception module, a digital reception signalfrom the signal received from the bus and outputting the digitalreception signal to the second terminal, outputting, via the changeoverfeedback block, feedback regarding a changeover of the operating modethat has taken place based on the operating mode changeover signal, thechangeover feedback block outputting the feedback to the communicationcontrol device via the second terminal and in the digital receptionsignal.

The method yields the same advantages as stated above with regard to thetransceiver device and/or the communication control device.

Further possible implementations of the present invention also includecombinations, even if not explicitly stated, of features or specificembodiments described above or discussed below with regard to theexemplary embodiments. Those skilled in the art will also add individualaspects as enhancements or supplements to the particular basic form ofthe present invention, in view of the disclosure herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described in greater detail below withreference to the figures, and based on exemplary embodiments.

FIG. 1 shows a simplified block diagram of a bus system according to afirst exemplary embodiment of the present invention.

FIG. 2 shows a diagram for illustrating the design of messages that maybe sent from user stations of the bus system according to the firstexemplary embodiment of the present invention.

FIG. 3 shows a simplified schematic block diagram of a user station ofthe bus system according to the first exemplary embodiment of thepresent invention.

FIGS. 4 through 6 show an example of signals in the first exemplaryembodiment with regard to feedback of an operating mode changeover ofthe transceiver device in a user station that acts only as a receiverduring a second communication phase (data phase).

FIGS. 7 through 9 show an example of signals in the first exemplaryembodiment with regard to feedback of an operating mode changeover ofthe transceiver device in a user station that acts as a sender during asecond communication phase (data phase).

FIGS. 10 through 12 show an example of signals in the first exemplaryembodiment with regard to feedback of an operating mode changeover ofthe transceiver device in a user station, which after the secondcommunication phase (data phase) is changed over into the operating modefor the first communication phase (arbitration phase).

Unless stated otherwise, identical or functionally equivalent elementsare provided with the same reference numerals in the figures.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

FIG. 1 shows as an example a bus system 1 that is in particular thebasis for the design of a CAN bus system, a CAN FD bus system, a CAN FDsuccessor bus system, and/or modifications thereof, as described below.Bus system 1 may be used in a vehicle, in particular a motor vehicle, anaircraft, etc., or in a hospital, and so forth.

In FIG. 1 , bus system 1 includes a plurality of user stations 10, 20,30, each of which is connected to a first bus wire 41 and a second buswire 42 at a bus 40. Bus wires 41, 42 may also be referred to as CAN_Hand CAN_L, and are used for electrical signal transfer after coupling-inthe dominant levels or generating recessive levels for a signal in thetransmission state. Messages 45, 46 in the form of signals are seriallytransferable between individual user stations 10, 20, 30 via bus 40.User stations 10, 20, 30 are, for example, control units, sensors,display devices, etc., of a motor vehicle.

As shown in FIG. 1 , user station 10 includes a communication controldevice 11, a transceiver device 12, and a changeover feedback block 15.In contrast, user station 20 includes a communication control device 21and a transceiver device 22. User station 30 includes a communicationcontrol device 31, a transceiver device 32, and a changeover feedbackblock 35. Transceiver devices 12, 22, 32 of user stations 10, 20, 30 areeach directly connected to bus 40, although this is not illustrated inFIG. 1 .

In each user station 10, 20, 30, messages 45, 46 are encoded in the formof frames via a TXD line and an RXD line, and are exchanged bitwisebetween particular communication control device 11, 21, 31 andassociated transceiver device 12, 22, 32. This is described in greaterdetail below.

Communication control devices 11, 21, 31 are each used for controlling acommunication of particular user station 10, 20, 30 via bus 40 with atleast one other user station of user stations 10, 20, 30 connected tobus 40.

Communication control devices 11, 31 create and read first messages 45,which are modified CAN messages 45, for example, and also referred tobelow as CAN XL messages 45. Modified CAN messages 45 or CAN XL messages45 are built up based on a CAN FD successor format, described in greaterdetail with reference to FIG. 2 . Communication control devices 11, 31may also be designed to provide a CAN XL message 45 or a CAN FD message46 for transceiver devices 12, 32 or receive it from same, as needed.Communication control devices 11, 31 thus create and read a firstmessage 45 or second message 46, first and second messages 45, 46differing by their data transfer standard, namely, CAN XL or CAN FD inthis case.

Communication control device 21 may be designed as a conventional CANprotocol controller or CAN controller according to ISO 11898-1:2015, inparticular as a CAN FD-tolerant conventional CAN controller or a CAN FDcontroller. Communication control device 21 creates and reads secondmessages 46, for example conventional CAN messages or CAN FD messages46. CAN FD messages 46 may include a number from 0 to up to 64 databytes, which in addition are transferred at a much faster data rate thanthat of a conventional CAN message. In the latter case, communicationcontrol device 21 is designed as a conventional CAN FD controller.

Except for the differences described in greater detail below,transceiver devices 12, 32 may be designed as CAN XL transceivers.Additionally or alternatively, transceiver devices 12, 32 may bedesigned as a conventional CAN FD transceiver. Transceiver device 22 maybe designed as a conventional CAN transceiver or as a CAN FDtransceiver.

A formation and then transfer of messages 45 having the CAN XL format,in addition to the reception of such messages 45, is achievable by useof the two user stations 10, 30.

FIG. 2 shows for message 45 a CAN XL frame 450, which is transmittedfrom transceiver device 12 or transceiver device 32. For the CANcommunication on bus 40, CAN XL frame 450 is divided into differentcommunication phases 451 through 455, namely, an arbitration phase 451,a first changeover phase 452 situated at the end of arbitration phase451, a data phase 453, a second changeover phase 454 situated at the endof data phase 453, and a frame end phase 455.

In arbitration phase 451, for example at the start a bit is transmitted,which is also referred to as an SOF bit and which indicates the start offrame. An identifier including 11 bits, for example, for identifying thesender of message 45 is also transmitted in arbitration phase 451.During the arbitration, with the aid of the identifier, bitwisenegotiation is carried out between user stations 10, 20, 30 concerningwhich user station 10, 20, 30 would like to transmit message 45, 46having the highest priority, and therefore for the next time period fortransmitting in changeover phase 452 and subsequent data phase 453,obtains exclusive access to bus 40 of bus system 1.

In the present exemplary embodiment, in first changeover phase 452preparation is made for the changeover from arbitration phase 451 intodata phase 453. Changeover phase 452 may include a bit AL1 that has bitduration T_B1 of a bit of arbitration phase 451, and that is transmittedwith the physical layer of arbitration phase 451. The physical layercorresponds to the bit transmission layer or layer one of theconventional Open Systems Interconnection (OSI) model.

In data phase 453, after a DH1 bit and a DL1 bit, a data fieldidentifier that is 8 bits long, for example, and that identifies thetype of content in the data field may be initially transmitted. Forexample, the data field identifier may contain the value 9, whichstates, for example, that a data packet that is built up according toInternet Protocol version 4 (IPv4) is present in the data field.Following the data field identifier, for example a data length code thatis 11 bits long may be sent, which may take on, for example, values from1 to up to 2048, or some other value by an increment of 1.Alternatively, the data length code may include fewer or more bits, sothat the value range and the increment may take on other values. Thedata length code is followed by further fields, for example the headercheck sum field. The useful data of CAN XL frame 450 or of message 45,also referred to as the data field of message 45, are subsequently sent.The useful data may include data, corresponding to the value range ofthe data length code, for example with a number of up to 2048 bytes or alarger number of bytes or some other arbitrary number of pieces of data.A check sum of the data of data phase 453 and of the data of arbitrationphase 451 may be contained at the end of data phase 453, for example ina check sum field. The sender of message 45 may insert stuff bits as aninverse bit into the data stream in each case after a predeterminednumber of identical bits, in particular 10 identical bits. Inparticular, the check sum is a frame check sum F_CRC via which all bitsof frame 450 up to the check sum field are verified. This may befollowed by an FCP field having a predetermined value, for example 1100.

In the present exemplary embodiment, in second changeover phase 454preparation is made for the changeover from data phase 453 into frameend phase 455. A piece of protocol format information that is containedin at least one bit and is suitable for implementing the changeover issent. Changeover phase 454 may include a bit AH1 that has bit durationTB_1 of a bit of arbitration phase 451, but that is transmitted with thephysical layer of data phase 453.

In frame end phase 455, after two bits AL2, AH2 at least one acknowledgebit ACK may be contained in an end field in frame end phase 455. Thismay be followed by a sequence of 7 identical bits that indicate the endof CAN XL frame 450. By use of the at least one acknowledge bit ACK, itmay be communicated whether or not a receiver has found an error inreceived CAN XL frame 450 or message 45.

A physical layer, similarly as with CAN and CAN FD, is used at least inarbitration phase 451 and frame end phase 455. In addition, in firstchangeover phase 452 a physical layer, similarly as with CAN and CAN FD,may be used at least in part, i.e., at the start. Furthermore, in secondchangeover phase 454 a physical layer, similarly as with CAN and CAN FD,may be used at least in part, i.e., at the end.

An important point during phases 451, 455, at the start of phase 452 andat the end of phase 454, is that the conventional CSMA/CR method isused, which allows simultaneous access of user stations 10, 20, 30 tobus 40 without destroying higher-priority message 45, 46. It is thuspossible to add further bus user stations 10, 20, 30 to bus system 1 ina relatively simple manner, which is very advantageous.

Consequently, the CSMA/CR method must provide so-called recessive stateson bus 40, which may be overwritten by other user stations 10, 20, 30with dominant states on bus 40.

The arbitration at the start of a frame 450 or of message 45, 46, andthe acknowledgement in frame end phase 455 of frame 450 or of message45, 46, are possible only when the bit time is much more than twice aslong as the signal propagation time between two arbitrary user stations10, 20, 30 of bus system 1.

Therefore, the bit rate in arbitration phase 451, frame end phase 455,and at least partially in changeover phases 452, 454, is selected to beslower than in data phase 453 of frame 450. In particular, the bit ratein phases 451, 452, 454, 455 is selected as 500 kbit/s, resulting in abit time of approximately 2 ps, whereas the bit rate in data phase 453is selected as 5 to 10 Mbit/s or greater, resulting in a bit time ofapproximately 0.1 ps and shorter. The bit time of the signal in theother communication phases 451, 452, 454, 455 is thus greater than thebit time of the signal in data phase 453 by at least a factor of 10.

A sender of message 45, for example user station 10, starts atransmission of bits of changeover phase 452 and of subsequent dataphase 453 onto bus 40 only after user station 10, as the sender, has wonthe arbitration, and user station 10, as the sender, thus has exclusiveaccess to bus 40 of bus system 1 for sending. The sender may eitherswitch to the faster bit rate and/or the other physical layer after aportion of changeover phase 452, or may switch to the faster bit rateand/or the other physical layer only with the first bit, i.e., at thestart, of subsequent data phase 453.

In general, in the bus system with CAN XL, in comparison to CAN or CANFD in particular the following differing properties may be achieved:

-   -   a) acquiring and optionally adapting proven properties that are        responsible for the robustness and user-friendliness of CAN and        CAN FD, in particular a frame structure including identifier and        arbitration according to the CSMA/CR method,    -   b) increasing the net data transfer rate to approximately 10        megabits per second, and    -   c) increasing the quantity of the useful data per frame to        approximately 2 kbytes or some other arbitrary value.

FIG. 3 shows the basic design of user station 10 together withcommunication control device 11, transceiver device 12, and changeoverfeedback block 15. User station 30 has a similar design, as shown inFIG. 3 , except that block 35 is provided separately from communicationcontrol device 31 and transceiver device 32. Therefore, user station 30and block 35 are not separately described. The functions of changeoverfeedback block 15 described below are present in an identical form forchangeover feedback block 35.

According to FIG. 3 , communication control device 11 also includes acommunication control module 111, a transmission signal output driver112, and an RxD terminal configuration module 113. Communication controldevice 11 is designed as a microcontroller or includes amicrocontroller. Communication control device 11 processes signals of anarbitrary application, for example a control unit for a motor, a safetysystem for a machine or a vehicle, or other applications.

However, FIG. 3 does not show a system application-specific integratedcircuit (ASIC), which alternatively may be a system base chip (SBC) onwhich multiple functions necessary for an electronics assembly of userstation 10 are combined. Among other things, transceiver device 12 andan energy supply device (not illustrated) that supplies transceiverdevice 12 with electrical energy may be installed in the system ASIC.The energy supply device generally supplies a voltage CAN_Supply of 5 V.However, depending on the requirements, the energy supply device maysupply some other voltage having a different value and/or may bedesigned as a power source.

According to FIG. 3 , transceiver device 12 also includes a transmissionmodule 121, a reception module 122, a driver 123 for transmission signalTxD, a reception signal output driver 124, a driver 125 that outputs asignal RxD_TC to changeover block 126, and a changeover block 126.Changeover block 126 forms from signal RxD_TC, signal TxD, and a signalS_SW, which is the output signal of reception module 122, an operatingstate switching signal S_OP for switching transmission module 121. Inaddition, changeover block 126 forms from signal RxD_TC and signals TxD,S SW an operating state switching signal S_OPT for switching receptionthresholds of reception module 122. Changeover block 126 recognizes thatsignaling from communication control module 111 is present in thatchangeover block 126 compares signal RxD_TC and signal S_SW, sincesignal RxD_TC contains at least one pulse according to a signal RxD_Kthat is sent from communication control module 111. This is described ingreater detail below with reference to FIGS. 4 through 12 .

Transmission module 121 from FIG. 3 is also referred to as atransmitter. Reception module 122 is also referred to as a receiver. Theuse of signal TxD in changeover block 126 is optional, as also shown inFIG. 3 by the dashed line at signal TxD. Signal RxD and signal RxD_TChave identical signal patterns, the two signals being separated by adriver 125.

Changeover block 126 may be designed as a switching block which inparticular includes at least one flip-flop.

Changeover feedback block 15 includes an operating mode detection module151 and an operating mode feedback module 152, whose functions aredescribed in greater detail below.

Even though transceiver device 12 is consistently referred to below, itis alternatively possible to provide reception module 122 in a separatedevice externally from transmission module 121. Transmission module 121and reception module 122 may be designed as a conventional transceiverdevice 22. Transmission module 121 may in particular include at leastone operational amplifier and/or one transistor. Reception module 122may in particular include at least one operational amplifier and/or onetransistor.

As shown in FIG. 3 , transceiver device 12 is connected to bus 40, ormore precisely, to its first bus wire 41 for CAN_H and its second buswire 42 for CAN_L. In transceiver device 12, first and second bus wires41, 42 are connected to transmission module 121 and to reception module122. The supplying of voltage for the energy supply device for supplyingfirst and second bus wires 41, 42 with electrical energy takes place ina customary manner. In addition, the connection to ground or CAN GND isachieved in a customary manner. The same applies for the termination offirst and second bus wires 41, 42 via a terminating resistor.

During operation of bus system 1, transmission module 121 converts atransmission signal TxD of communication control device 11 intocorresponding signals CAN_H and CAN_L for bus wires 41, 42 when userstation 10 acts as a sender, and transmits these signals CAN_H and CAN_Lonto bus 40. Even though signals CAN_H and CAN_L are stated here fortransceiver device 12, with regard to message 45 they are to beunderstood as signals CAN XL_H and CAN XL_L, which in data phase 453differ from conventional signals CAN_H and CAN_L in at least onefeature, in particular with regard to the formation of the bus statesfor the various data states of signal TxD and/or with regard to thevoltage or the physical layer and/or the bit rate.

A difference signal VDIFF=CAN_H−CAN_L is formed on bus 40 as a result ofthe signals. With the exception of an idle or standby state, transceiverdevice 12 with reception module 122 during normal operation alwayslistens to a transfer of data or messages 45, 46 on bus 40, inparticular regardless of whether or not user station 10 is the sender ofmessage 45. Reception module 122 forms a signal S_SW and passes it on tocommunication control device 11 as a digital reception signal RxD viareception signal output driver 124, as shown in FIG. 3 .

At the end of arbitration phase 451, it is clear which of user stations10, 30 in subsequent data phase 453 acts as a sender, and which actsonly as a receiver. In the present example, user station 10 acts as asender and also as a receiver, while user station 30 acts only as areceiver. However, user station 30 may of course alternatively be thesender.

Changeover block 126 is designed to recognize, in a received message 45from bus 40, the start of particular changeover phases 452, 454 andthen, depending on the function of user station 10 in the subsequentcommunication phase, to change over the properties of transceiver device12. Changeover block 126 may change over between the following operatingmodes of transceiver device 12:

a) first operating mode: Z_SL=transmit/receive properties forarbitration phase 451,

-   -   transmission module 121 in transceiver device 12 generates        dominant and recessive states on bus 40,    -   reception module 122 operates with a reception threshold T_a of        typically approximately 0.7 V. In addition, reception module        122, in particular for integration of user station 10 into an        ongoing communication at bus 40, may operate with a negative        reception threshold.    -   b) second operating mode: transmit/receive properties for data        phase 453 as a receiver (reception node),        -   transmission module 121 in transceiver device 12 generates            recessive states or is optionally switched off after            changeover phase 452, since transceiver device 12 is not a            sender, and acts only as a receiver of message 45 or of a            frame 450,        -   reception module 122 operates with a reception threshold T_d            of typically approximately 0.0 V.    -   c) third operating mode: transmit/receive properties for data        phase 453 as a sender (transmission node),    -   transmission module 121 in transceiver device 12 drives a 0        state or a 1 state as a function of the TxD signal, since        transceiver device 12 acts as a sender of message 45 or of a        frame 450,    -   reception module 122 operates with a reception threshold T_d of        typically approximately 0.0 V.

RxD terminal configuration module 113 of communication control device 11configures terminal RxD according to the necessary communicationdirection, using signals S1, S2 at the input of module 113, as describedbelow. Signal S1 may be referred to as RxD_out_ena, which allows nodriving of additional signal RxD_TC via the RxD terminal (first terminaloperating mode), or allows driving of additional signal RxD_TC via theRxD terminal (second terminal operating mode). Signal S2 may be referredto as RxD_out_val. Depending on the value of signal S2, communicationcontrol device 11 drives terminal RxD at the changeover points in timebetween the two different communication phases for signaling totransceiver device 12 the operating mode to be set, i.e., on the onehand in first changeover phase 452 for changing over between arbitrationphase 451 and data phase 453, and on the other hand, in secondchangeover phase 454 for changing over between data phase 453 and frameend phase 455. Depending on the value of signal S2, communicationcontrol device 11 may optionally drive terminal RxD in a third terminaloperating mode, also referred to as “talk mode,” in which an internalcommunication between devices 11, 12 is possible. Otherwise, as iscustomary with CAN, terminal RxD is an input, i.e., not an output, forcommunication control device 11, as described above, so thatcommunication control device 11 does not drive terminal RxD. TerminalRxD may thus be operated bidirectionally with the aid of RxD terminalconfiguration module 113 and signals S1, S2. In other words, terminalRxD is a bidirectional terminal.

For this purpose, communication control device 11 and output driver 124are designed in such a way that during driving for the purpose ofsignaling, communication control device 11 drives terminal RxD morestrongly than output driver 124. This avoids the situation that thevalue of the RxD line could be uncertain if both communication controldevice 11 and output driver 124 drive terminal RxD, resulting in asuperimposition of the two signal sources at terminal RxD. In the eventof such a superimposition of the two signal sources at terminal RxD,communication control device 11 always prevails. The value of the RxDline is thus always certain.

Changeover block 126 may thus provide the option to set in transceiverdevice 12 one of the at least three operating modes mentioned above,which are signaled via the RxD terminal and TxD terminal. An additionalterminal in the form of another pin at transceiver device 12, and thusalso at communication control device 11, is not necessary for thispurpose.

For this purpose, according to FIG. 3 , changeover block 126 is providedwith at least two inputs via which a signal RxD_TC, signal SSW, andoptionally signal TxD are fed into changeover block 126. Signal RxD_TCis based on a signal that is sent from communication control device 11,via the terminal for the RxD signal, to transceiver device 12. Withsignal RxD_TC, communication control device 11 signals to transceiverdevice 12 at least that transceiver device 12 is now to make thechangeover into the appropriate operating mode for data phase 453. Inaddition, with signal RxD_TC and/or signal TxD, communication controldevice 11 signals to transceiver device 12 into which of operating modesZ_F_RX, Z_F_TX the changeover is to be made. This is helpful inparticular for the changeover from arbitration phase 451 to data phase453. At the end of data phase 453, communication control device 11 withsignal RxD_TC may carry out the signaling for the changeover oftransceiver device 12 from each of the two operating modes of data phase453 into operating mode Z_SL for arbitration phase 451. Furthermore,with signal RxD_TC, arbitrary other pieces of information may be sentfrom communication control device 11 to transceiver device 12, asmentioned above.

According to FIG. 3 , transceiver device 12 leads signal RxD_TC fromterminal RxD, via driver 125, to the terminal of changeover block 126for signal RxD_TC. In contrast, signal S_SW is generated from the signalreceived from bus 40. Signal RxD_TC is led between the terminal for theRxD signal and the output of reception signal driver 124 to changeoverblock 126. Signal S_SW is led from the output of reception module 122and, upstream from the input of reception signal driver 124, tochangeover block 126.

If changeover block 126 recognizes changeover phase 452, the operatingstate of transmission module 121 and/or of reception module 122, andthus the operating mode of transceiver device 12, are switched viasignals S_OP, S_OPT that are output from changeover block 126.

At changeover feedback block 15, based on the output signals oftransmission module 121 and of reception module 122, operating modedetection module 151 detects which operating mode Z SL, Z_F_RX, Z_F_ZXtransmission module 121 and reception module 122 are switched into. Inparticular, operating mode detection module 151 is designed as acomparator. Operating mode detection module 151 passes on the detectionresult as a status signal S_E to operating mode feedback module 152.Operating mode feedback module 152 also receives a status signal S_Bfrom changeover block 126. Status signal S B indicates whether asignaling of the changeover condition has been recognized. Optionally,status signal S_B additionally indicates which operating mode is to beswitched into. With the aid of these status signals S_E, S_B, operatingmode feedback module 152 decides whether operating mode feedback module152, via an RxD signal, must provide feedback to communication controldevice 11, and when the feedback must be sent.

If the feedback is positive, i.e., transceiver device 12 has recognizedthe signaling and has changed over the operating mode as requested,operating mode feedback module 152 then changes or manipulates the RxDsignal in such a way that communication control device 11 obtains thefeedback via the RxD signal.

Transceiver devices 12, 32 have at least three different options forcarrying out the feedback via an RxD signal. This is described ingreater detail below with reference to FIGS. 4 through 12 . It isassumed that user station 10 acts as a sender (transmission node) fordata phase 453, and user station 30 acts only as a receiver (receptionnode) for data phase 453.

FIGS. 4 through 6 show an example of signals before, during, and afterchangeover phase 452 for user station 30 (transmission node). At thetransition from arbitration phase 451 to data phase 453, in changeoverphase 452 a changeover is made from a bit duration T_B1 of arbitrationphase 451 to a smaller or shorter bit duration T_B2 of data phase 453.Operating mode Z_SL of transceiver device 32 is changed over intooperating mode Z_F_RX of transceiver device 32.

To this end, FIG. 4 shows an example of an RxD_K signal that is drivenby communication control device 31 for the changeover of the operatingmode of transceiver device 32, in each case for states 0, Z, 1. State Zstands for the high-impedance state. FIG. 5 shows a portion oftransmission signal TxD_R, which for example is provided bycommunication control device 31 for transceiver device 32. FIG. 6 showsa signal RxD_R that is driven from transceiver device 32 tocommunication control device 31. Signal RxD_R is made up of the digitalsignal, which has been generated from signal S_SW, and the signal whichthe operating mode feedback module, which corresponds to module 152,outputs to transceiver device 32. In addition, signal RxD_R alsoincludes the signaling with the aid of signal RxD_K; signal RxD_Koverwrites signal RxD_R, as indicated in FIG. 6 as pulse RxD_TC,AH_1.

As shown in FIGS. 4 through 6 , prior to changeover phase 452, intransmission signal TxD_R communication control device 31 sends in eachcase a state high (first binary signal state), so that transmissionsignal TxD_R does not overwrite the signal states on bus 40, whichaccording to signal RxD_R from FIG. 6 are an FDF bit and an XLF bit insuccession, each with the state high (first binary signal state), andthen a resXL bit and an AL1 bit, each with the state low (second binarysignal state). Alternatively, operating mode changeover block 126 isdesigned to switch off transmission module 121 in second operating modeZ_F_RX.

At the end of arbitration phase 451, based on signal RxD_K from FIG. 4 achangeover is made from the bits of arbitration phase 451 with bit timeT_B1 to the shorter bits of data phase 453 with bit time T_B2, as shownin FIGS. 4 through 6 . For this purpose, RxD_K or resulting signalRxD_TC includes at least one pulse or a pulse pattern AH_1 in the AL1bit. The duration of a pulse of pulse pattern AH_1 from FIG. 4 issmaller or greater than bit time T_B2. The duration of a pulse of pulsepattern AH_1 from FIG. 4 is smaller or shorter than bit time T_B1. TheAL1 bit is followed by the data of data phase 453.

According to FIGS. 4 through 6 , feedback R S takes place using module152 after the RXD signaling with at least one pulse or pulse patternAH_1 of signal RxD_K or RxD_TC in the AL1 bit, and after the actualchangeover of the operating mode of transceiver device 32 has takenplace. The changeover into second operating mode Z_F_RX means thattransceiver device 32 changes over its reception threshold T_a in itsreception module 122 into reception threshold T_d. The signal pattern ofsignal RxD_R without feedback R_S from transceiver device 32 is depictedin FIG. 6 by solid lines. The signal pattern of feedback R_S fromtransceiver device 32 is depicted in FIG. 6 by boldface lines.

In the example from FIG. 6 , as feedback R_S, transceiver device 32inserts into the signal pattern of signal RxD_R an inverse pulse thatlasts at bus 40 up to one of the subsequent edge changes. In FIG. 6 ,feedback R_S lasts up to the next rising edge in the digital signal,which has been generated from signal S_SW. In particular, the inversepulse has an absolute duration of 400 ns, for example. Of course, someother duration of the inverse pulse of signal RxD_R is possible.

If communication control device 31, more precisely, its module 111,samples the AL1 bit in reception signal RxD_R for a sampling point oftypically 80%, for example, and sees a logical “1”, the changeover intransceiver device 32 has been correctly carried out. If communicationcontrol device 31, more precisely, its module 111, sees a logical “0”,then the changeover in transceiver device 32 has not been correctlycarried out.

If the changeover has not worked and feedback R_S is absent, an error ispresent. For example, transceiver device 32 remains in the operatingmode for the first communication phase (longer bit durations), althoughfor the second communication phase (shorter bit durations) it shouldhave changed into operating mode Z_F_RX. There is a high likelihood thatcommunication control device 31 will now find bit errors in the bitstream of signal RxD via the second terminal due to the fact that thereception threshold in reception module 122 has not changed over to T_d.If communication control device 31 sees bit errors in the bit stream ofsignal RxD via the second terminal, during the subsequent errorprocessing, communication control device 31 does not have to switchtransceiver device 32 into operating mode Z_SL for the firstcommunication phase (longer bit durations), since transceiver device 32is already in this operating mode.

If the changeover of the operating mode in transceiver device 32 hasworked and this has been correctly signaled with the aid of the signalpattern of feedback R S, communication control device 31 knows thattransceiver device 32 is in operating mode Z_F_RX. If communicationcontrol device 31 finds a bit error in the bit stream of signal RxD viathe second terminal, during the subsequent error processing,communication control device 31 must be able to intentionally changeover transceiver device 32 from an operating mode of the secondcommunication phase (longer bit duration) into an operating mode of thefirst communication phase (shorter bit duration), in particular with apulse on the TXD signal. Therefore, it is not necessary to wait for thelong-duration “timeouts” in transceiver device 32, which likewise switchthe operating mode back to the operating mode of the first communicationphase. As a result, transceiver device 32 (reception node), despitereception errors, is able to recognize the idle condition of 11recessive bits at the end of a sent frame 450, and is thus able tore-integrate very quickly back into the communication on bus 40.

In addition, it is optionally possible for user station 30 to send anerror frame in order to abort the transfer of frame 450 or message 45.The transfer using incorrectly set bus components may thus bediscontinued as quickly as possible. This increases the net data ratethat is transferable in bus system 1, and the communication in bussystem 1 becomes more robust.

FIGS. 7 through 9 show an example of feedback R_S in user station 10(transmission node) during the changeover in transceiver device 12 fromoperating mode Z_SL to third operating mode Z_F_TX. Except for thefollowing differences, the description above with reference to FIGS. 4through 6 applies.

FIG. 7 shows an example of an RxD_K signal that is driven bycommunication control device 11 for the changeover of the operating modeof transceiver device 12, in each case for states 0,Z, 1. FIG. 8 shows aportion of transmission signal TxD_T, which for example is provided bycommunication control device 11 for transceiver device 12. FIG. 9 showsa signal RxD_T which, after receipt of transmission signal TxD_T at theterminal for reception module 122, is driven by transceiver device 12 tocommunication control device 11. Signal RxD_T is made up of the digitalsignal that has been generated from signal S_SW, and the signal thatoperating mode feedback module 152 outputs to transceiver device 12. Inaddition, signal RxD_T also includes the signaling with the aid ofsignal RxD_K; signal RxD_K overwrites signal RxD_R, as indicated in FIG.9 as pulse RxD_TC,AH_1.

As shown in FIGS. 7 through 9 , prior to changeover phase 452,communication control device 11 sends in transmission signal TxD_T theFDF bit and an XLF bit in succession, each with the state high (firstbinary signal state). This is followed by an resXL bit, which is sentwith the state low (second binary signal state) and followed by an AL1bit, which is likewise sent with the state low (second binary signalstate).

According to FIGS. 7 through 9 , feedback R_S takes place after theactual changeover of the operating mode of transceiver device 12. Moreprecisely, feedback R_S takes place during the change into thirdoperating mode Z_F_TX, after the end of the AL1 bit. The signal patternof digital reception signal RxD_T without feedback from transceiverdevice 12 is depicted in FIG. 9 by solid lines. The signal pattern offeedback R_S from transceiver device 12 is depicted in FIG. 9 byboldface lines.

In the example from FIG. 9 , as feedback R_S, transceiver device 12likewise inserts into the signal pattern of signal RxD_T an inversepulse that is made up in such a way that a pulse at the S_SW signal isfiltered out. The pulse length is determined by the two edge changes inthe S_SW signal. In other words, operating mode feedback module 152inserts the pulse as feedback R_S in such a way that the pulse indigital reception signal RxD_T overwrites a value that has an arbitrarylength or duration and is the inverse of the value of the pulse. Theedges in reception signal RxD_T limit the duration of the value of thepulse. As a result, digital reception signal RxD_T is changed; i.e.,operating mode feedback module 152 filters out the next 0 pulse from theRxD bit stream at the second terminal. Alternatively, the next 1 pulsecould also be filtered out from the RxD bit stream at the secondterminal. Alternatively, more than one pulse may be filtered out.

Transceiver device 12 filters out the first 0 pulse, regardless of itslength, in digital reception signal RxD_T after the changeover, i.e.,the first 0 pulse after the end of the AL1 bit. Communication controldevice 11 notices this manipulation or change of digital receptionsignal RxD_T during sampling of the bits of signal RxD_T. This delayedfeedback R_S is sufficient, since communication control device 11, inparticular its module 111, does not abort the sending of message 45 andit is possible to respond to an error even a couple of bits later.

Depending on what is indicated by feedback R_S of the changeover,communication control device 11 may follow the procedure as stated abovewith regard to communication control device 31.

FIGS. 10 through FIG. 12 show an example of feedback R_S in user station30 (reception node) during the changeover in transceiver device 32 fromsecond operating mode Z_F_RX to first operating mode Z_SL. Thischangeover thus takes place after data phase 453.

FIG. 10 shows an example of an RxD_K signal that is driven bycommunication control device 11 for the changeover of the operating modeof transceiver device 32, in each case for states 0, Z, 1. FIG. 11 showsa portion of transmission signal TxD_R, which for example is provided bycommunication control device 11 for transceiver device 32, as describedabove with reference to FIG. 5 . However, an AH1 bit with the state high(first binary signal state) in changeover phase 454, and then in frameend phase 455, an AL2 bit with the state low (second binary signalstate) and an AH2 bit with the state high (first binary signal state),are now sent via bus 40. These are followed by the other bits of frameend phase 455. FIG. 12 shows a signal RxD_R that is driven fromtransceiver device 32 to communication control device 31, as describedabove with reference to FIG. 6 . In FIG. 12 , signal RxD_R also includesthe signaling with the aid of signal RxD_K; signal RxD_K overwritessignal RxD_R, as indicated in FIG. 12 as pulse RxD_TC,AH_1 and explainedabove with reference to FIG. 6 .

FIG. 12 shows two options for feedback R_S. Thus, feedback R_S may takeplace prior to the actual changeover of the operating mode oftransceiver device 32, as shown via the pulse with a boldface line inthe AH1 bit as feedback R_S. Alternatively, feedback R_S may take placeafter the actual changeover of the operating mode of transceiver device32, as shown via the pulse with a boldface line in the AL2 bit asfeedback R_S. The changeover of the operating mode takes place at theend of the AH1 bit. The signal pattern of digital reception signal RxD_Rwithout feedback from transceiver device 32 is depicted in FIG. 12 bysolid lines.

In the example from FIG. 12 , as feedback R_S, transceiver device 32inserts an inverse pulse of 200 ns, for example, into the signal patternof signal RxD_R. Of course, some other duration of the pulse of feedbackR_S is selectable.

Feedback R_S in the AL2 bit according to FIG. 12 is more advantageousthan feedback R_S in the AH1 bit according to FIG. 12 , since feedbackR_S in the AL2 bit does not interfere with the synchronization of userstations 10, 30 at the edge between the AH1 bit and the AL2 bit.

The same feedback is also possible in user station 10 (transmissionnode) when transceiver device 32 switches from operating mode Z_F_TXinto operating mode Z_SL.

As a result of the design of user station 10 described above, a galvanicconnection via an additional terminal in each case at communicationcontrol device 11 and transceiver device 12 connected thereto is notnecessary in order for communication control device 11 to be able totransfer the point in time of the operating mode changeover and receivefeedback R_S. This means that block 15 advantageously does not requirean additional terminal, which is not available at a standard housing oftransceiver device 12. Changing to another housing that is larger andexpensive in order to provide an additional terminal is thus notnecessary due to block 15.

In addition, block 15 makes it possible for transceiver device 12 to notrequire a protocol controller functionality. Such a protocol controllercould, among other things, recognize changeover phase 452 of message 45and initiate data phase 453 as a function thereof. However, since suchan additional protocol controller would require considerable surfacearea in transceiver device 12 or the ASIC, block 15 results in a greatreduction in the resource requirements.

As a result, the interconnection of operating mode changeover block 126and block 15 with a customary transceiver device provides a very simpleand cost-effective approach to indicate to transceiver device 12 that achangeover, and which changeover between its various operating modes, isto be made, namely, in particular from the first operating mode into thesecond operating mode or from the first operating mode into the thirdoperating mode or from the second operating mode into the firstoperating mode or some other changeover of operating modes. In addition,block 15 may also provide communication control device 12 [sic; 11] withappropriate feedback R_S regarding the changeover in a very simple,cost-effective, and robust manner.

Due to the described design of transceiver device(s) 12, 32, much higherdata rates may be achieved in data phase 452 [sic];

than with CAN or CAN FD. In addition, the data length in the data fieldof data phase 453 may be arbitrarily selected, as described above. As aresult, the advantages of CAN with regard to the arbitration may bemaintained, yet a higher volume of data may be transferred very reliablyand thus effectively, in a shorter time period than previously, i.e.,without the need for repeating the data on account of an error, asexplained below.

A further advantage is that error frames are not needed in bus system 1for the transfer of messages 45, but may be optionally used. If no errorframes are used, messages 45 are no longer destroyed, which eliminatesthe need for a duplicate transfer of messages, thus increasing the netdata rate.

If the bus system is not a CAN bus system, operating mode changeoverblock 126 may be designed to respond to other changeover signals. Thesame applies for block 15. In this case, operating mode changeover block126 may switch transmission module 121 and/or reception module 122 intoone of at least two different operating modes based on a result of itsevaluation, and after expiration of a duration T0 that is preset foroperating mode changeover block 126, may change at least one of theoperating modes over into another of the operating modes. Block 15 mayin each case provide communication control device 11 with appropriatefeedback R S regarding the changeover.

According to a second exemplary embodiment, block 15, more precisely,its module 152, sends a pulse pattern to the RXD terminal. For example,if RXD=0 at that time, particular transceiver device 12, 32 may thentransmit pulse pattern 010 to terminal RXD.

Alternatively, block 15, more precisely, its module 152, sends a pulsepattern to the RXD terminal with a time delay. For example, block 15,more precisely, its module 152, may send the pulse pattern to bus 40only after the next edge.

Otherwise, bus system 1 in the second exemplary embodiment has the samedesign as described above with regard to the first exemplary embodiment.

According to a third exemplary embodiment, block 15, more precisely, itsmodule 152, sends the signal to terminal RXD:=“constant 0 or constant 1”up to a predetermined event.

The predetermined event may be a new signaling of the changeover fromcommunication control device 11, 31 to associated transceiver device 12,32. Alternatively, the predetermined event is a predetermined timeout intransceiver device 12, 32.

Thus, as long as transceiver device 12, 32 is in a predetermined state,“RXD=constant” applies for its RXD terminal. If transceiver device 12,32 leaves the predetermined state, the RxD signal of transceiver device12, 32 once again corresponds to the value on bus 40.

Thus, each of transceiver devices 12, 32 has at least three differentoptions for carrying out feedback R S using reception signal RxD, RxD_R,RxD_T. For this purpose, each of transceiver devices 12, 32 ofassociated communication control device 11, 31 provides a receptionsignal RxD, RxD_R, RxD_T, which does not reflect the state on bus 40 asis customary, but which instead is at least temporarily manipulated.Based on the manipulation, communication control device 11, 31, inparticular its module 111, recognizes positive feedback R_S fromassociated transceiver device 12, 32.

All of the above-described embodiments of blocks 15, 35, of userstations 10, 20, 30, of bus system 1, and of the method carried outtherein may be used alone or in any possible combination. In particular,all features of the above-described exemplary embodiments and/ormodifications thereof may be arbitrarily combined. Additionally oralternatively, in particular the following modifications are possible.

Although the present invention is described above with the example ofthe CAN bus system, the present invention may be employed for anycommunications network and/or communication method in which twodifferent communication phases are used in which the bus states, whichare generated for the different communication phases, differ. Inparticular, the present invention is usable for developments of otherserial communications networks, such as Ethernet and/or 10BASE-TISEthernet, field bus systems, etc.

Above-described bus system 1 according to the exemplary embodiments isdescribed with reference to a bus system based on the CAN protocol.However, bus system 1 according to the exemplary embodiments may also besome other type of communications network in which data are seriallytransferable at two different bit rates. It is advantageous, but not amandatory requirement, that in bus system 1, exclusive, collision-freeaccess of a user station 10, 20, 30 to a shared channel is ensured, atleast for certain time periods.

The number and arrangement of user stations 10, 20, 30 in bus system 1of the exemplary embodiments is arbitrary. In particular, user station20 in bus system 1 may be dispensed with. It is possible for one or moreof user stations 10 or 30 to be present in bus system 1. It is possiblefor all user stations in bus system 1 to have the same design, i.e., foronly user station 10 or only user station 30 to be present.

The type of signaling of the changeover of the operating mode toindividual transceiver devices 12, 32 is arbitrarily selectable.Additionally or alternatively, the type of feedback R_S for eachindividual transceiver device 12, 32 is arbitrarily selectable. Inaddition, feedback R_S for the changeover from arbitration phase 451into data phase 453 may be different from feedback R_S for thechangeover from data phase 453 into arbitration phase 451. Arbitrarycombinations of the above-described embodiment variants of feedback R_Sare possible.

1-16. (canceled)
 17. A transceiver device for a user station of a serialbus system, the transceiver device comprising: a first terminalconfigured to receive a transmission signal from a communication controldevice; a transmission module configured to transmit the transmissionsignal onto a bus of the bus system, in which bus system at least onefirst communication phase and one second communication phase are usedfor exchanging messages between user stations of the bus system; areception module configured to receive a signal from the bus, thereception module being configured to generate a digital reception signalfrom the signal received from the bus; a second terminal configured tosend the digital reception signal to the communication control deviceand to receive an operating mode changeover signal from thecommunication control device; and a changeover feedback block configuredto output feedback regarding a changeover of an operating mode that hastaken place as a result of the operating mode changeover signal, thechangeover feedback block being configured to output the feedback to thecommunication control device via the second terminal and in the digitalreception signal.
 18. The transceiver device as recited in claim 17,wherein the changeover feedback block includes: an operating modedetection module configured to detect, based on output signals of thetransmission module and of the reception module, which operating modethe transmission module and the reception module are switched into; andan operating mode feedback module configured to evaluate an operatingmode status signal that is output by the operating mode detectionmodule, and to evaluate a status signal of an operating mode changeoverblock that is configured to carry out the changeover of the operatingmode based on the operating mode changeover signal.
 19. The transceiverdevice as recited in claim 18, wherein the operating mode feedbackmodule is configured to decide whether the operating mode feedbackmodule must provide the feedback to the communication control device viathe digital reception signal, and when the feedback must be sent. 20.The transceiver device as recited in claim 18, wherein: the operatingmode feedback module is configured to insert the feedback into thedigital reception signal after the changeover of the operating mode thathas been signaled via the operating mode changeover signal, or theoperating mode feedback module is configured to insert the feedback intothe digital reception signal after the operating mode changeover signal,but before the changeover of the operating mode that has been signaledvia the operating mode changeover signal.
 21. The transceiver device asrecited in claim 18, wherein the operating mode feedback module isconfigured to insert the feedback into the digital reception signal asat least one pulse having a value that is an inverse of a value of thedigital reception, the pulse having a predetermined absolute duration orthe pulse is configured in such a way that the pulse in the digitalreception signal overwrites a value whose duration in the digitalreception signal is limited by a distance between two arbitrary edges ofthe digital reception signal.
 22. The transceiver device as recited inclaim 21, wherein the at least one pulse lasts at the bus up to asubsequent edge change that follows in the digital reception signal. 23.The transceiver device as recited in claim 18, wherein the operatingmode feedback module is configured to configure the feedback asmanipulation of the digital reception signal in such a way that thedigital reception signal has a constant value up to a predeterminedevent.
 24. The transceiver device as recited in claim 23, wherein thepredetermined event is: (i) a new signaling of the changeover of theoperating mode, using the operating mode changeover signal, or (ii) apredetermined passage of time in the transceiver device.
 25. Thetransceiver device as recited in claim 21, further comprising: anoperating mode changeover block configured to evaluate the operatingmode changeover signal that is received from the communication controldevice at the second terminal and to evaluate the transmission signal,the operating mode changeover block being configured to switch thetransmission module and/or the reception module into one of at leastthree different operating modes based on a result of the evaluation. 26.The transceiver device as recited in claim 25, wherein the operatingmode changeover signal received from the communication control device atthe second terminal is a pulse having a value that is an inverse of avalue of the digital reception signal, the operating mode changeoverblock being configured to switch the reception module from a firstoperating mode into a second operating mode when the changeover signalincludes the pulse, and a value of the transmission signal correspondsto a value of the pulse, the operating mode changeover block beingconfigured to switch the transmission module and the reception modulefrom the first operating mode into a third operating mode when thechangeover signal includes the pulse and the value of the transmissionsignal is an inverse of the value of the pulse, the transceiver devicein the second operating mode not being a sender of a message in thesecond communication phase, and the transceiver device in the thirdoperating mode being the sender of the message in the secondcommunication phase.
 27. A communication control device for a userstation of a serial bus system, comprising: a communication controlmodule configured to generate a transmission signal for controlling acommunication of the user station with at least one other user stationof the bus system, in which bus system at least one first communicationphase and one second communication phase being used for exchangingmessages between user stations of the bus system; a first terminalconfigured to send the transmission signal to a transceiver device whichis configured to transmit the transmission signal onto a bus of the bussystem; and a second terminal configured to receive a digital receptionsignal from the transceiver device; wherein the communication controldevice is configured to generate an additional signal that indicates tothe transceiver device that a switch is to be made from a presentoperating mode into another operating mode of at least three differentoperating modes, and that achieves an internal communication between thecommunication control module and the transceiver device, and thecommunication control module is configured to send the additionalsignal, in the digital reception signal, to the transceiver device viathe second terminal, and to receive, via the second terminal, feedbackin the digital reception signal from the transceiver device regarding achangeover of the operating mode that has taken place as a result of theadditional signal, and to evaluate the feedback.
 28. The transceiverdevice as recited in claim 17, wherein the transmission module isconfigured to drive bits of the transmission signal onto the bus in thefirst communication phase with a first bit time that is longer by atleast a factor of 10 than a second bit time of bits that are driven bythe transmission module onto the bus in the second communication phase,wherein the operating mode changeover signal, via the second terminalfor signaling that the changeover of the operating mode is to be made,includes: (i) at least one pulse with a duration that is shorter thanthe first bit time and longer than the second bit time, or (ii) at leastone pulse with a pulse duration that is approximately equal to thesecond bit time or shorter than the second bit time, and wherein thefeedback via the second terminal for signaling that the operating modehas been changed over includes: (i) at least one pulse with a durationthat is shorter than the first bit time and longer than the second bittime, or (ii) at least one pulse with a pulse duration that isapproximately equal to the second bit time or shorter than the secondbit time.
 29. The transceiver device as recited in claim 17, wherein thesignal received from the bus in the first communication phase isgenerated with a different physical layer than the signal received fromthe bus in the second communication phase.
 30. The transceiver device asrecited in claim 17, wherein in the first communication phase, it isnegotiated which of the user stations of the bus system in a subsequentsecond communication phase obtains, at least temporarily, exclusive,collision-free access to the bus.
 31. bus system, comprising: a bus; andat least two user stations that are connected to one another via the busin such a way that they may communicate serially with one another, andof which at least one of the user stations includes: a communicationcontrol device, a first terminal configured to receive a transmissionsignal from the communication control device, a transmission moduleconfigured to transmit the transmission signal onto a bus of the bussystem, in which bus system at least one first communication phase andone second communication phase are used for exchanging messages betweenuser stations of the bus system, a reception module configured toreceive a signal from the bus, the reception module being configured togenerate a digital reception signal from the signal received from thebus, a second terminal configured to send the digital reception signalto the communication control device and to receive an operating modechangeover signal from the communication control device, and achangeover feedback block configured to output feedback regarding achangeover of an operating mode that has taken place as a result of theoperating mode changeover signal, the changeover feedback block beingconfigured to output the feedback to the communication control devicevia the second terminal and in the digital reception signal.
 32. Amethod for communicating in a serial bus system, the method beingcarried out using a transceiver device for a user station of a bussystem, in which at least one first communication phase and one secondcommunication phase are used for exchanging messages between userstations of the bus system, the user station including a transmissionmodule, a reception module, a changeover feedback block, a firstterminal, and a second terminal, and the method comprising the followingsteps: receiving, via the reception module, a signal from the bus of thebus system; generating, via the reception module, a digital receptionsignal from the signal received from the bus and outputting the digitalreception signal to the second terminal; outputting, via the changeoverfeedback block, feedback regarding a changeover of an operating modethat has taken place based on an operating mode changeover signal, thechangeover feedback block outputting the feedback to the communicationcontrol device via the second terminal and in the digital receptionsignal.